With the continuous deepening of research on semiconductor luminescent materials, the continuous advancement of LED manufacturing technology and the development and application of new materials, the development of LED has made breakthrough progress, and the price has also dropped drastically. Scholars from all countries are concerned. Especially after the successful development of ultra-high brightness LED, it is widely used in the research of plant physiology or cultivation, such as photomorphogenesis, photosynthesis and chlorophyll synthesis research. 1. LED characteristics applied to plant facility cultivation Light is one of the basic factors for plant growth and development. Light quality has a regulatory effect on plant growth, morphogenesis, photosynthesis, material metabolism and gene expression. Controlling plant morphogenesis and growth is an important technology in the field of facility cultivation through light quality regulation. The light sources used in the cultivation of traditional plant facilities are generally fluorescent lamps, metal halide lamps, high pressure sodium lamps and incandescent lamps. These light sources are selected according to the adaptability of the human eye to light. The spectrum has many unnecessary wavelengths and has little effect on plant growth. As the fourth generation of new lighting source, LED has the advantages of energy saving, environmental protection, safety and reliability, long service life, short response time, small size, light weight, low heat generation, easy dispersion or combined control, and many other important characteristics different from other electric light sources. . With the innovation of optoelectronic technology and the decrease of production cost, LED has become the first choice light source in the field of plant facility cultivation because of the following excellent performance: (1) The spectral performance is good, and pure monochromatic light and composite spectrum can be obtained as needed, and the spectral width is less than ± At 30 nm, the wavelength coincides with the spectral range of plant photosynthetic and photomorphological formation; (2) the effective utilization of light energy can reach 80% to 90%, and can achieve separate control of different light quality and luminous intensity; (3) as a cold light source It can irradiate plants at close range and greatly improve the utilization efficiency of space. It can be used in multi-layer cultivation three-dimensional combination system to achieve low heat load and miniaturization of production space; (4) LED is impact resistant, not easily broken, contains no mercury, no pollution Waste can be recycled, the service life is dozens of times of ordinary light source, and the extra durability also reduces operating costs. Due to these remarkable features, LEDs are well suited for plant cultivation in controlled facility environments such as plant tissue culture, facility horticulture and lock-up plant plants, and aerospace eco-life insurance systems. However, due to the current high price of LEDs, there is still a need to promote the application of plant facilities. However, with the rapid development of LEDs in the direction of high brightness and low price, LEDs will be widely used in the field of plant cultivation in the near future. 2, LED applied to plant tissue culture In plant tissue culture, photosynthetic photon flux density (PPFD: Photosynthetic PhotonFluxDensity), photoperiod and spectral distribution play an important role in plant photosynthesis and morphogenesis. Plant tissue culture mainly relies on electric light source. The traditional electric light source has extremely low bio-efficiency and high calorific value for plants, and light electricity accounts for about 65% of the total electricity cost. It is one of the highest non-labor costs in plant tissue culture. Therefore, using LED to provide illumination in plant tissue culture, regulating light quality and PPFD can not only regulate the growth and morphogenesis of tissue culture plants, shorten the culture period, improve the quality, but also greatly reduce energy consumption and reduce costs. (1) Effects of red light (620-660 nm) and far red light (710-740 nm) LED on the growth of tissue culture plants The ratio of red light to far red light flux (R/FR) in the spectrum has an important influence on plant morphogenesis and plant height adjustment. The R/FR ratio has become an important evaluation parameter for controlling plant morphology. Fujiwara and other studies found that among the LED light sources, red LEDs and far red LED light sources are more likely to affect the light form formation and growth of tissue culture seedlings than fluorescent lamps. Tanaka et al. found that red LED promoted leaf growth of orchid tissue culture seedlings but reduced chlorophyll content, stem and root dry weight. Lian et al. showed that under the irradiation of red LED alone, the growth index and dry matter accumulation of lily bulbs were lower, which was related to the low CO2 assimilation caused by red light alone. This result confirms the results of Goins et al.'s application of red LEDs to wheat photosynthetic yield. However, reports of the effects of red or far-red LEDs on the growth of tissue culture plants are not consistent. Miyashita et al. found that with the increase of PPFD of red LED, the stems of potato tissue cultured stems increased, and the chlorophyll content also increased, but there was no significant difference in leaf area and dry weight. Nhut et al. showed that under the irradiation of red LED, strawberry tissue cultured leaves stretched, petiole elongation, stem elongation, but chlorophyll content decreased. Kim and other researches believe that under the treatment of single red LED or red LED + far red LED, excessive elongation of chrysanthemum tissue culture stems leads to fragile stems, and other important growth indicators are also reduced, which is generally not conducive to the normal growth and development of plants. . Hahn et al. found the inhibitory effect of red LED on the stem growth of the tissue culture seedlings. These phenomena are believed to be that monochromatic red light causes an imbalance in the distribution of light energy available to photosystems I and II, thus inhibiting stem growth. In addition, in the experimental results of different light quality LEDs with PPFD of 45μmol/(m2·s) for the treatment of orchid protocorm small pieces, it was found that red LED treatment is the most effective for inducing callus from protocorm segments. of. General junction box consists of box cover, box body, wiring terminal, diode, connecting line and connector. 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